Positive and negative feedback systems are the principles of of the endocrine system and there effects upon each other and target organs.

Generally, “releasing” hormones are between the hypothalamus and adenohypophysis, and “stimulating” hormones are between the pituitary and other major endocrine glands. Build up of a and hormone tells the hypothalamus and pituitary to “slow down” production. It is important to understand the difference between POSITIVE and NEGATIVE feedback.

Overall cellular mechanisms of action of the two major classes of hormones, polypeptide and steroid.

All three lobes of the pituitary: Anterior, intermediate, and posterior lobes. Note that the pituitary also has a “portal” circulation, i.e., artery  capillaries  veins  capillaries, rather than just a  c  v. Why? Ans: to create a “secondary” circulation between the pituitary and the hypothalamis releasing factors!

The differentiation between acidophils and basophils is usually not too difficult unless the stain is really lousy. Chromophobes are uncommon, and have minimal cytoplasm and no granules. Chromophobe cytoplasm stains close to basophil cytoplasm in color, but is less granular and has is a minimal cytoplasm.

The normal weight of the thyroid , in grams, is also the same as its 24 hour radioactive iodine uptake percentage. Why? Ans: Because it take up 1% per gram.

Find the colloid, follicular cells, and para-follicular cells (also known as C cells or light cells)

If there was such a thing as a hypothalamic adenoma producing excessive TRF (thyroid releasing factor), would this be tertiary hyperthyroidism? Ans: Yes. Would an adenoma or a carcinoma more likely produce hyperthyroidism? Ans: Adenoma Why?

The diagnosis of Hashimoto thyroiditis requires not only lymphoid follicles in the thyroid, but SECONDARY (i.e., germinal centers) follicles should be present.

NO scalloping

Scalloping

Podiatric case of the week.

Decreased Iodine leads to decreased thyroid hormone, which leads to increased TSH which leads to increased growth of follicles. That’s how an iodine deficiency leads to a goiter.

Many vegetables are goiterogens, fruits are NOT.

Most goiters worldwide are due to iodine deficiency. Why? Ans: The thyroid enlarges to try to trap more iodine, when serum levels are low. This is a adaptive response.

Every type of thyroid disorder known is more common in females than males? Why? Ans: unknown What is the difference between a cold and a not-cold nodule isotopically?

Did you ever know anybody who died from thyroid cancer? Why not?

EXTREMELY well encapsulated tumor. Benign.

EXTREMELY well encapsulated tumor. Benign.

Note the resemblance of H ü rthle cells to oncocytes, oxyphil cells, gastric parietal cells and apocrine cells, i.e., very bright red and abundant cytoplasm. In general however, please remember that “ATYPIA” in benign endocrine neoplasms is VERY COMMON, and, in contrast with other organ systems of the body, ususlly does NOT imply malignancy or PRE-malignancy!

EXTREMELY NON well encapsulated tumor. Malignant. Thyroid tissue can look perfectly normal, but come out of bone or liver? In contrast with marked atypia seen in BENIGN endocrine neoplasms, often NO ATYPIA is seen with malignant endocrine neoplasms, and invasion or metastases is often the only evidence that endocrine tissue is malignant.

Papillary neoplasms do NOT usually look uniform on cut surface.

To make things simple, let’s just say you can regard ALL papillary thyroid neoplasms as benign.

Orphan Annie cells are papillary carcinoma of the thyroid cells in which considerably cytoplasm has invaginated into the nucleus.

Is amyloid a type of “Hyaline”? What are some other types? What is hyaline?

This is just a generality, not a law.

Find the chief cells, find the oxyphil cells, find the fat.

PTH stimulates osteoclasts to chew up bone and transfer calcium from the bone to the serum “compartments”.

Hyperparathyroidism symptoms are the same as hypercalcemia symptoms, and vice versa.

Hypoparathyroidism symptoms are the same as hypocalcemia symptoms, and vice versa.

Is this a right or a left adrenal gland? Ans: LEFT Why: Right is usually flatter and much less triangular. Think of the liver as squishing it.

85.
ADRENAL MEDULLA <ul><li>PHEOCHROMOCYTOMAS , aka, primary tumors of the adrenal medulla </li></ul><ul><ul><li>10% arise in an MEN setting </li></ul></ul><ul><ul><li>10% are EXTRA-adrenal </li></ul></ul><ul><ul><li>10% are bilateral </li></ul></ul><ul><ul><li>10% are malignant </li></ul></ul><ul><ul><li>10% are in childhood </li></ul></ul><ul><ul><li>You can only call them malignant if they metastasize </li></ul></ul>www.freelivedoctor.com

87.
TWO crucially important points specific for endocrine tumors: <ul><li>1. FUNCTIONING carcinomas are very RARE in ANY endocrine gland. Why? (KEY principle of oncology) </li></ul><ul><li>2. Benign adenomas may have extremely bizarre nuclei, but are most usually BENIGN!!! </li></ul>www.freelivedoctor.com